1. Field of the Invention
The present invention relates to a printing apparatus, a printing system, and a prediction method of the usage of a printing agent that can be configured to predict, prior to the development processing of a printing image (to-be-printed image), the usage of the printing agent (e.g., ink) required for the printing.
2. Description of the Related Art
A printing apparatus requires a printing agent (e.g., ink) in order to provide printing to a printing medium. One ink supply method is, for example, an on-demand supply method (also called as pit in method) for a serial scan type printing apparatus in which a carriage having a reciprocating movement in a main scanning direction includes an ink jet printing head. This method is a method in which, only when ink needs to be supplied to a tank included in the carriage (sub tank), ink is supplied from a tank (main tank) in a printing apparatus body to the sub tank by allowing the sub tank to communicate with the main tank.
Generally, when such an ink supply method is practically used, the sub tank has a capacity for retaining the ink amount for providing the printing (printing of solid image for one to two page(s) or more) based on full address data for one to two page(s) or more of a printing medium, for example. When the ink amount in the sub tank is reduced, ink is appropriately supplied from the main tank.
A conventional method for controlling the timing at which ink is supplied in such an ink jet printing apparatus is disclosed in Japanese Patent Application Laid-open No. 7-032606 (1995). In this method, printing data to be printed next printing is previously read to count, based on the printing data, a planned ejection number of ink droplets at the next printing, thereby calculating, based on the count value, a planned ink use amount at the next printing. Then, the planned ink use amount is compared with the amount of ink currently remaining in the sub tank. When the former amount is smaller than the latter amount, ink is supplied to the sub tank.
Japanese Patent Application Laid-open No. 2002-059569 also suggests a method in which the time required for the processing for developing image data is saved by using an easier processing to predict the ejection number of ink droplets at the next printing. In this method, the attribute information regarding image contents previously specified at the printing is referred so that the ejection number of ink droplets is predicted based on this information. The ejection number is used for determining whether ink supply is required or not.
Recently, improvement of a processing function of a printer and diversification of data formats that can be processed by a printer have gradually enabled the printing processing having a more complicated layout than that assumed by the above conventional techniques.
For example, there have been an increased number of cases in which, when a digital camera or a cell phone or the like is connected to use various image sources for printing, the printing must be performed in accordance with an arbitrary layout (e.g., index layout, seal layout, home page layout). In such a case, a single page in particular must have thereon a plurality of pieces of information for image, character, and/or graphic object information. Thus, it has been difficult to estimate the contents of the image to be printed when only the attribute information of the image is available.
In the case of a layout in which a single page has thereon such a plurality of pieces of object information, when all of these pieces of object information are developed to be previously processed so that the planned ink use amount is calculated more accurately, a factor such as the speed of a communication interface causes the significant increase of the printing time. This causes a risk in which the printing operation may be performed for such a long time that deteriorates the practicality. An increased printing resolution and an improved image quality of image source preparation machines (e.g., digital camera) in particular have allowed the size of data (e.g., image data) to increase continuously. Due to this reason, an index layout in which these images are arranged for example requires an enormous amount of time for merely reading the image data.
On the other hand, regular printing operations have a tendency where a time required for the printing for one page has been reduced continuously. Thus, the long-time processing as described above is a demerit to a user, causing the corresponding product specification to be not suitable for a practical use. The same particularly applies to a printing apparatus using an on-demand ink supply method as described above.
Specifically, in the printing apparatus using the on-demand ink supply method, the number of times at which ink is supplied from a main tank to a sub tank is increased (i.e., the number of times at which communication and blocking between these tanks are performed is increased), which causes an increase in the amount of ink consumed for operations other than the image printing. In order to suppress such ink consumption for operations other than the image printing, the sub tank needs to have an increased capacity. However, this causes a carriage driving mechanism including therein the sub tank to have a larger size and/or causes the limitation to a high-speed driving of the carriage. In order to minimize the number of times at which ink is supplied from the main tank to the sub tank to suppress the consumption of ink used for operations other than the image printing, planned ink use amount may be accurately calculated by using the processing time for a longtime. However, in this case, the long-time processing is a demerit to a user, causing the corresponding product specification to be not suitable for a practical use.